CA2841393C - Satellite communication system, leo satellite relaying communications between a geo satellite and terrestrial stations, the uplinks and downlinks using the same frequency band andtime-division multiplexing - Google Patents

Abstract

The present invention relates to a payload (10) for a repeater satellite (LEO) of a communication system, said repeater satellite being placed into drift orbit above the surface of a celestial body, and said payload (10) being configured to repeat data received from a stationary satellite (GEO) above the surface of the celestial body towards a terminal (REC) substantially at the surface of the celestial body, and to repeat data received from the terminal towards the stationary satellite. The payload (10) is further configured to use a single frequency band for repeating data towards the stationary satellite (GEO), referred to as uplink transmission, and for repeating data towards the terminal (REC), referred to as downlink transmission, as well as to time-division multiplex the uplink transmissions and the downlink transmissions. The present invention also relates to a telecommunication system comprising a repeater satellite provided with a payload (10) according to the invention, as well as to a satellite communication method.

Description

SATELLITE COMMUNICATION SYSTEM, A LEO SATELLITE RELAYING
COMMUNICATIONS BETWEEN A GEO SATELLITE AND LAND STATIONS, CONNECTIONS

AMOUNTS AND DESCENDANTS USING THE SAME FREQUENCY BAND AND THE
TIME MULTIPLEXING
Field of the invention The invention relates to the field of transmission systems of long distance data. It concerns more particularly the systems and methods of data communications (data transfer, remote control, terminal tracking ...) between users with small mobile terminals.
Context of the invention and problem The issue of long distance data transmission from or to a mobile terminal, arises especially for links between computers (machine to machine or M2M). This area of transmission is then characterized by a much lower need for data throughput only for image-type links or the Internet, and / or the ability to use intermittent rather than continuous linkage We know a first approach to this problem, followed by existing data transmission systems such as Orbcomm and Argos, which use constellations of satellites in low orbit (LEO of English Low Earth Orbit). In this approach, the normal mode of operation of each low LEO satellite requires that it be, on the one hand in the simultaneous visibility of a ground control station and connection, and on the other hand a user terminal.
The satellite serves as a communication link between the two parties, and the latency of acknowledgments and messages is function the distance between the satellite and the ground station (GES of English Gateway Earth Station).
However, the coverage provided by the ground station network of systems using low-orbiting satellites, such as Orbcomm and Argos, is limited by the deployment of ground stations (GES) and existing systems only provide limited Earth coverage in this mode.
Each ground station allows coverage over a radius of about 3000 km, and each of these systems comprises about twenty ground stations.

2 It is easy to see that the blanket areas present large white areas for which the system is not usable.
These areas cover in particular a large part of the ocean areas, a significant part of continental areas such as Africa or Australia.
In cases where the LEO satellite has no visibility simultaneous user terminal and ground control station (GES), it is is necessary to use a method of communication of storage and sending type (Method known to those skilled in the art under the name store & forward). In this method, the message is stored aboard the satellite, which continues its moving on its orbit until it flies over the GES ground station at which it delivers the stored message.
With this method of operation, communication delays are long and make bidirectional communications difficult in acceptable conditions, since deadlines are typically understood between a few minutes and the 100 to 150 minutes duration of an orbit complete LEO satellite.
In addition, there are examples of hybrid telecommunications for the transmission of data users. These hybrid systems are composed of satellites geostationaries and a satellite constellation in low orbit.
There may be mentioned a first patent document US 6208625.
This document describes a network of LEO satellites and geostationaries (GEO) able to communicate with each other. On the ground, user terminals are capable of receiving / transmitting (Rx / Tx) with LEO and GEO satellites. LEO component performs traffic filtering received from the terminals, and depending on the urgency of the traffic received, it this traffic is internally to the LEO or to the GEO.
In a second patent document EP 0883252, it is proposed a satellite communication system allowing global coverage, a reduction in the transmission delay (Tx), and a maximization of use the capacity of the system (broadband satellite the interconnection of several constellations in medium orbit ¨ ME0 ¨ and geostationary ¨ GEO ¨).

3 The ME0 and GEO satellites communicate directly with each other via inter-satellite links, allowing traffic routing (for voice and for data) on board satellites according to certain rules.
In addition, this document proposes sharing and reuse of the spectrum between GEO and ME0 satellites at very high frequencies (eg between 40 and 60 GHz), to enable the function known as seamless handover for portable devices (network crossing mobile to a fixed network without ongoing communication interruption).
It is clear that current hybrid systems have a great deal of complexity, synonymous with high cost of implementation and use.
Objectives of the invention An object of the invention is to provide a solution based on repeater satellites as simple as possible, offering good performances (link budget, availability) within the coverage of each satellite.
Presentation of the invention According to a first aspect, the present invention relates to a useful satellite repeater of a telecommunications system, said satellite repeater being intended to be placed in moving orbit over the area of a celestial body, and the payload being configured to repeat data received from a stationary satellite above the surface of the celestial body towards a terminal substantially on the surface of the celestial body, and to repeat data received from the terminal to the stationary satellite. Said payload is further configured for:
- use the same frequency band for the repetition of data to the stationary satellite, so-called rising emission, and for the repetition of data to the terminal, said transmission descending, and - multiplex over time the emissions and downlink emissions.
Such provisions allow a better sharing of power boarded the repeater satellite. In addition, such provisions optimize the payload architecture to reduce its cost manufacturing, congestion and / or launch mass.

4 It should be noted that by terminal is meant substantially on the surface of the celestial body, including terrestrial, maritime user terminals or aeronautical. Similarly, said terminals are admitted to be for example placed in land, sea or aeronautical means.
We give below specific modes of realization of the load useful satellite repeater. The invention is also aimed at all combinations technically possible of these particular embodiments.
According to a particular embodiment, the payload comprises at less a power amplifier, and said payload is configured for use said power amplifier for both broadcasts rising and for downlink transmissions.
According to a particular embodiment, the payload comprises:
- at least one rising transmission antenna, at least one downlink transmitting antenna, means for routing a signal at the output of the amplifier of power, representative of data to be repeated, or to said transmitting antenna rising towards said transmitting antenna down.
According to one particular embodiment, the payload comprises means for multiplexing, at the input of the power amplifier, signals emissions and downlink signals.
According to a particular embodiment, the payload comprises:
- several downward transmitting antennas, means for routing a signal at the output of the amplifier of power, representative of data to be repeated, towards one any of said downward transmitting antennas.
According to a particular embodiment, the payload is configured to use the same frequency band used for broadcasts and downward transmissions, for the receipt of data at repeating the terminal, so-called uplink reception, and for receiving data to be repeated from the stationary satellite, called downward reception.
According to a particular embodiment, the payload comprises several uplink antennas, and said payload is configured to simultaneously receive on each of said receiving antennas uplink.
According to a particular embodiment, the payload is configured to multiplex over time the emissions and receptions

5 rising, and / or to multiplex in time the broadcasts down and downward receptions.
According to a particular embodiment, the payload is configured to use the same first frequency subband of the band of frequency for uplinks and uplinks, and use the same second frequency sub-band of the frequency band for downward receptions and downward transmissions.
According to a particular embodiment, the payload is configured to perform upward receptions simultaneously with broadcasts descendants, and to perform downward receptions simultaneously rising emissions.
According to a second aspect, the present invention relates to a system telecommunications network, intended for the transfer of data between at least one terminal, located substantially on the surface of a celestial body, and at least one stationary satellite above the surface of the celestial body. The system comprises one or more satellite signal repeaters, said satellites repeaters passing above the surface of the celestial body and having a payload according to the invention.
Specific embodiments of the system are given below.
telecommunications. The invention is also aimed at all combinations technically possible of these particular embodiments.
According to a particular embodiment, the same band of frequency for communications between terminals and the constellation of repeater satellites only for communications between the satellite stationary and the repeater satellite. Preferably, when the terminal is in the zone of coverage of the stationary satellite, the same band of frequency for direct communications between terminals and the satellite stationary.

6 This provides a significant advantage over the solutions of art prior. The frequency band used by the system can be located in any of the bands allocated to telecommunications services satellites (low bands, for example UHF or VHF, up to high frequencies such as Ka or Q bands). Preferably, the band of frequencies used is the L band (between 0.9 and 2.0 GHz) which is more particularly suitable for mobile satellite communications.
According to a particular embodiment, the system comprises less a ground station connecting stationary satellites. The communications between ground and repeater satellites are provided by stationary satellites and connection stations of these stationary satellites. These communications include both data exchange between users and potentially communications remote control and telemetry of spatial rehearsal means. This embodiment therefore does not require the use of ground station of connection assigned to repeater satellites.
According to a particular embodiment, at least one satellite repeater is placed in polar or quasi-polar orbit (inclination of the orbit better than 70) around the celestial body.
According to a particular embodiment:
at least one repeater satellite comprises means for performing amplification without frequency translation of the signal received from the stationary satellite, - the air interface used is a CDMA interface (from English Division Multiple Access Code), - and at least one terminal has means for managing the arrival of two signals with differences in delay and Doppler.
In this case, preferentially, the means of managing the arrival of two signals with differences in delay and Doppler, of the terminal are a Rake type receiver, well known to those skilled in the art.
According to a particular embodiment:
the air interface is of the TDMA type, - the system uses two distinct signals: one for satellites

7 stationary and one for repeater satellites, - a time multiplexing is used to distribute the capacity between stationary satellites and repeater satellites with guard intervals and Doppler pre-compensation at repeater satellites.
According to a particular embodiment, at least one terminal includes ways to use spatial diversity or MIMO techniques (Multiple Input Multiple Output) to recombine the signals from the time a stationary satellite and a repeater satellite.
According to a particular embodiment:
at least one repeater satellite relays the signal, so transparent or regenerative, without frequency translation of the received signal, and the air interface comprises means for limiting the interference to the level of a terminal, between the signals coming from a satellite stationary and the signals relayed by a repeater satellite.
According to a particular embodiment:
at least one repeater satellite relays the signal, so transparent or regenerative, in an adjacent canal, before its reissue, and - the telecommunications system includes an entity of coordination to coordinate frequency plans between stationary satellites and repeater satellites.
According to a third aspect, the present invention relates to a method telecommunications system for the transfer of data between a terminal, located substantially on the surface of a celestial body, and a satellite stationary above the surface of the celestial body, the transfer of data between said terminal and said stationary satellite being effected via a satellite repeater configured to repeat data received from said satellite stationary to said terminal and to repeat data received from said terminal to said stationary satellite. In addition :
- the repeater satellite uses the same frequency band for the

8 repetition of data to the stationary satellite, said transmission rising, and for the repetition of data to the terminal, so-called downlink broadcast, - the repeater satellite multiplexes over time the broadcasts rising and falling emissions.
The following are specific modes of implementation of the telecommunications process. The invention is also aimed at all technically possible combinations of these particular modes of implementation.
artwork.
According to a particular mode of implementation, the satellite repeater uses the same power amplifier for both emissions rising and falling emissions.
According to a particular mode of implementation, the satellite repeater uses the same frequency band, used for uplink and downward transmissions, for receiving data to be repeated from terminal, so-called uplink reception, and for receiving data at repeat stationary satellite, called downward reception.
According to a particular mode of implementation, the satellite repeater multiplexes in time the rising emissions and the upward receptions, and / or said repeater satellite time-multiplexed broadcasts descending and descending receptions.
According to a particular mode of implementation, the satellite repeater performs downlink transmissions and receptions simultaneously rising, and simultaneously performs rising emissions and downward receptions.
According to a particular mode of implementation, the satellite repeater uses the same first frequency sub-band of the frequency band for uplifting and up-and-coming broadcasts, and uses the same second frequency sub-band of the frequency band for downward receptions and downward transmissions.
Brief description of the figures The aims and advantages of the invention will be better understood when reading of the description and figures of particular embodiments, given at WO 2012/17180

9 PCT / EP2012 / 060359 As non-limiting examples, and for which the figures represent:
- Figure 1: the general architecture of the system, - Figure 2: illustration of LEO moving satellites positions and stationary GEO on a planisphere, at a given moment, - Figure 3: a table of orders of magnitude of delays between signals from a GEO stationary satellite and a moving satellite LEO for different altitudes of LEO orbits, - Figure 4: the coverage areas of the LEO traveling satellites and stationary GEO of the constellation described, - Figure 5: an example of use of a frequency band in a system according to the invention, - Figure 6: a schematic representation of a payload of a LEO traveling satellite according to a preferred embodiment, FIGS. 7a and 7b: examples of temporal multiplexing of communications between a user terminal, a moving satellite LEO and a GEO stationary satellite, - Figure 8: a schematic representation of a payload according to a variant of the embodiment of FIG.
In these figures, identical references designate elements identical or similar.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
The architecture of a telecommunications system according to the invention is illustrated in Figures 1 and 2. As seen in these figures, the system proposed uses two satellite constellations.
The first constellation is composed of one or more satellites stationary (also called GEO in the following description).
In the present case, the system described here by way of example in no way limiting, is based on a constellation of three stationary satellites GE01, GE02, GE03 placed in geostationary orbit above the three zones principal continents (eg longitudes 265 E, 25 E, 145 E
respectively, as shown in Figure 2). Stationary satellites GE01, GE02, GE03 operate in the so-called MSS band L (1.5 / 1.7 GHz).
The constellation of stationary satellites GE01, GE02, GE03 is controlled by one or more ground control stations, arranged in view of the stationary satellites GE01, GE02, GE03 which they control, which perform the functions of control and remote control. The constellation of stationary satellites GE01, GE02, GE03 is connected 5 to terrestrial telecommunication networks by one or more stations of terrestrial GES connections, arranged for the GE01 stationary satellites, GE02, GE03 via a link FL (English Feeder Link), in a known manner in itself.
The system is completed by a second constellation of three

10 moving satellites in low or medium orbit (also called satellites LEO or MEO satellites), with orbits of altitudes typically understood between 400 and 20000 km, acting as repeater satellites. It's clear that the system can use a larger or smaller number of satellites in each of the constellations of LEO moving satellites and stationary GEOs, the difference being a more or less complete coverage of the Earth.
In the example described here, the moving satellites are assumed to be of the type LEO, and placed in a sun-synchronous orbit at a altitude of 567 km with a tilt of 97.7 in three orbital planes different (with straight ascents of the ascending node at 0, 60 and 120).
It is recalled that the sun-synchronous orbit is defined by the fact that each passing satellite, after several orbits, for the same point of the Earth at the same local solar time. This system uses three satellites in low orbit: LE01, LE02, LE03, whose traces of orbits are illustrated in Figure 2 by way of non-limiting example.
In this example, these three satellites in LE01 low orbit, LE02, LE03, could be passenger payloads on satellites whose main payload is dedicated to another mission such as, for example, the observation of the Earth.
It is clear that the constellation of LE01, LE02 LE03, may include satellites moving in orbits of altitudes or different inclinations.
These moving satellites LE01, LE02, LE03, operate in the same frequency band than stationary satellites GE01, GE02, GE03, and

11 in the present case, in the MSS band L (1.5 / 1.7 GHz).
The telecommunications system is for any user, including mobile on the surface of the Earth, and with a terminal transmission / reception (also called REC terminal).
In the example illustrated in Figure 1, the system is addressed in particular to a user equipped with a transmission / reception terminal REC1, transmitting or receiving data from or to another user, possibly itself equipped with a transmission / reception terminal REC2, and also possibly mobile on the surface of the Earth. The user REC3 can also be connected to a terrestrial network (IP, PSTN, ...) and be connected to the user REC1 via the GES.
Each user terminal REC1 and REC2, is a terminal transportable, including a user interface, for example keyboard type, touch screen or data link to equipment electronics, a battery and / or power supply means, a processor and / or control electronics, memory storage means programs or data, and means of transmitting and receiving signals, operating in the MSS L frequency band, in the present example described here in no way limiting.
Each user terminal REC1 and REC2 is equipped in the present example of an omnidirectional antenna, adapted to receive signals emanating indifferently from any of the moving satellites LE01, LE02, LE03 in low orbit, or any of the stationary GE01 satellites, GE02, GE03 in geostationary orbit.
In the implementation described here, each user terminal REC1 and REC2, for the first way, includes a well-known Rake receiver of the man of the art. Recall that a receiver Rake is a radio receiver, originally designed to compensate for the attenuation due to multiple paths radio waves for terrestrial systems. It is based on the concept that reflected signals can be distinguished (typically in the case of a use of a CDMA multiplexing technique) and so can be suitably combined by taking advantage of the multiple propagation. For the return path, GEO stationary satellites are

12 supposed transparent and the Rake receiver is positioned at the level of the GHGs (GEO satellite connection stations).
It should be noted, however, that in the case of stationary satellites GEO would be of the regenerative type, it would be necessary that they embark a Rake receiver (replacing the receiver placed at the level of the GHG).
A communication between two user terminals REC1, REC2, assumed for two LE01, LE02 moving satellites respectively, and same stationary satellite GE01, has several steps, as well as schematized in Figure 1:
the first user terminal REC1 sends a first signal Si towards the first satellite LE01 scrolling in low orbit, the satellite scrolling LE01, receives and amplifies the signal Si transmitted by the user terminal REC1 on the ground and transmits it as a signal S2 to stationary satellite GE01 in geostationary orbit, - the stationary satellite GE01 receives the signal S2 and, if the conditions allow it, the signal Si, and retransmits them as a signal S3 to the second low-orbiting LE02 satellite, either directly (with routing on the satellite) either by via the GES connection station. Si and S2 are processed by means of a receiver Rake either on board (in the hypothesis of an edge routing) at the level of the station GES
(this solution is preferred for reasons of simplification of the implementation).
the LE02 traveling satellite receives and amplifies the signal S3 emitted by the stationary satellite GE01 and transmits it as an S4 signal to the ground user terminal REC2.
the user terminal REC2 receives the signal S4 and potentially the signal S3 if conditions permit. A Rake receiver allows to recombine these two signals at the user terminal.
In a case involving user terminals for two stationary satellites GE01, GE02, the link between the two terminals

13 users furthermore includes a segment of communication between these satellites, for example but not limited to, through the intermediary of GHG connection stations and ground links or via a link direct inter-satellite GEO, if it exists.
Naturally, it is also possible to envisage to carry out a communication of a user REC1 having a terminal mobile transmitter / receiver, with another REC3 user connected through a conventional terrestrial telecommunications network (PSTN, IP, ...) via the GES connection station.
In that case :
the first user terminal REC1 sends a first signal Si towards the first satellite LE01 scrolling in low orbit, the satellite scrolling LE01, receives and amplifies the signal Si transmitted by the user terminal REC1 on the ground and transmits it as a signal S2 to stationary satellite GE01 in geostationary orbit, the stationary satellite GE01 receives the signal S2 and potentially the signal Si and retransmits it as a signal S5 to the station GHG connection the GES connection station receives the signal S5, (by combining when necessary the signals Si and S2 contained in S5 by means of a Rake receiver) and transmits it as a signal S6 to ground user terminal REC3 via a terrestrial network classic.
Note that in Figure 1, the direct links between the terminals REC1, REC2 and REC3 and the GE01 stationary satellite are not figured to simplify the figure.
Different approaches can be considered for the repeater spaceborne on a moving satellite LE01, LE02, LE03.
Let, preferably, a simple amplification without translation of frequency of the received signal from the GEO stationary satellite. However, this involves the use of an air interface capable of supporting the arrival of two signals with some differences in delay and Doppler. It is by

14 example the case of a CDMA type air interface (Code Division Multiple Access) associated with a Rake receiver.
Or, alternatively, the use of two distinct signals (one for the GEO stationary satellite and one for the LEO running satellite). It is by example possible to use a TDMA type air interface (Time Division Multiple Access), known per se, by considering either temporal multiplexing to divide the capacity between LEO and stationary satellites GEO
(with guard intervals and Doppler pre-compensation at of the LEO running satellite). Alternatively or in addition, it is also possible to use two different channels of the frequency band (one for the GEO stationary satellite and one for the LEO running satellite).
In the implementation described here by way of example, the first approach was selected because it offers a simple and effective solution.
It exploits the diversity of satellites because the signals coming from both LEO and stationary GEO satellites can be combined in a Rake receiver to get a better signal on noise. This technique, improving the signal-to-noise ratio, allows to obtain a lower bit error rate, a more low power transmitted EIRP (Effective Isotropically Radiated Power), or a larger margin in the link budget.
Moreover, for a user terminal REC, in view simultaneously of a LEO moving satellite and a GEO stationary satellite, if the conditions of propagation cause the loss of a link to one of the satellites on which he is connected (due to the evolution of the geometry of the link with the satellite scrolling LEO varying with time, or because of obstacles in the line of sight of one of the two satellites parading LEO and stationary GEO), the other link can help maintain communication.
This concept of simple amplification without frequency translation of the signal received from the stationary GEO satellite, can be implemented by means of possibility offered by the Rake receiver, included in the user terminal REC
to combine different signals from different paths coming from a LEO moving satellite and a GEO stationary satellite.

In the satellite data communications scenario, which makes the object of the present implementation, the multipath component is generally negligible. In this case, the Rake receiver is used simply to combine several direct signals from 5 several LEO traveling and stationary GEO satellites, since the different Signals can be considered as path components fictitious multiples.
The received signals can then be combined in the terminal 10 user REC according to three main algorithms, known to the man of art and therefore not described further here:
- by a selection of the best signal (known as of selection combining), - by a simple equal combination of signals (known as

English term of equal gain combining), or - by a weighted recombination of the signals to maximize the total signal-to-noise ratio (known as Maximal Ratio Combining or MRC). This algorithm is the preferred solution because it is the most efficient in terms of ratio noise signal obtained.
One of the key issues related to the combination of signals is that each track followed has a length possibly very different because the relative position of the elements: user - satellite scrolling LEO -satellite stationary GEO. In order to balance the difference in propagation time, which also varies over time, appropriate data buffers must be provided at the Rake receiver. The sizing of these buffers depends on the delay difference in the worst case between different paths, and the maximum data transfer rate used.
In the proposed system, the time difference remains below 5 ms for the constellation of moving satellites LE01, LE02, LE03 envisaged.
The table in Figure 3 gives some orders of magnitude of time to different altitudes of low orbits compared to a stationary satellite GEO
in geostationary orbit.

16 It should also be noted that communication services envisaged for the system according to the invention, are preferentially low data rate transmissions. As a result, the buffer size of necessary data remains reasonable.
With this approach using a Rake receiver, in the case of a CDMA multiplexing technique, satellites moving LEO and stationary GEO share the same frequency band (MSS band L in the example) without generating harmful interference.
Frequency planning and coverage issues need to be also be taken into consideration, since the LEO coverage areas and GEO must be coordinated to ensure proper operation of the system. In the proposed approach, the coverage of stationary satellites GEO is composed of a global beam covering the entire surface visible from the Earth. This approach avoids or limits proceedings for LEO traveling satellites (known to those skilled in the art under the term hand over) between different beams from a (or many) GEO stationary satellites. LEO coverage is therefore included in the GEO coverage as shown in Figure 4. LEO running satellites so simply relay the signals from the GEO stationary satellites under which they are located.
In the example above:
- the LE01 satellite relaying the signals from and to the satellite stationary GE01, - the LE02 and LE03 traveling satellites relay the signals from and to the GE02 stationary satellite.
There is no LEO satellite in the satellite coverage Stationary GE03 at the moment shown in Figure 4. In fact, the satellite scrolling LE03 is, at this time, connected to the stationary satellite GE02.
As a moving LEO satellite moves in the coverage area of the GEO stationary satellites, it may be visibility of different GEO stationary satellites. However, we assume has at a given moment it is connected to a single geostationary satellite.
When

17 several GEO stationary satellites are in the visibility area of the LEO tracking satellites, different strategies can be adopted for the choice of the GEO stationary satellite to which the moving LEO satellite hang up (for example on a criterion of the best signal received at LEO moving satellite, or a geometric criterion of minimizing the distance between LEO moving satellite and GEO stationary satellite which is predictable by advance on the basis of the ephemeris satellites). In the example above the moving LEO satellite is connected to the GEO stationary satellite providing the best signal received.
With these assumptions, it is not necessary to conceive of complex scheduling strategies and all satellites (the three GEO stationary satellites and the three LEO running satellites) can operate for example on a single channel of the frequency band used, with multiplexing of the CDMA type.
Unlike the approach of the prior art type Orbcomm or Argos, the proposed system is able to provide communications from bidirectional data, based on the fact that the stationary satellite GEO
relays communications from LEO scrolling satellites.
According to this approach, as soon as the user terminal REC1, REC2 is in the coverage area of a LE01, LE02, LE03 moving satellite, it is possible to communicate bi-directionally and in real time with him.
he there is no longer any need for simultaneous visibility by the satellite moving LE01, LE02, LE03, the user terminal REC1, REC2 and a connection station ground, which allows to consider a complete coverage of the Earth.
The delay, to communicate with a user terminal REC1 on the ground is then only dependent on the frequency of passage of the satellites runners LE01, LE02, LE03, which depends directly on the orbit chosen for these satellites and the number of these satellites (up to continuous coverage of all the land).
FIG. 5 schematically represents the use, by a system according to the invention, of the same frequency band, for communications between REC user terminals and satellites

18 scrolling LEO, and for communications between said moving satellites LEO
and stationary GEO satellites.
FIG. 5 more particularly represents an example of use of the L-band for MSS type applications.
As shown in Figure 5, the L-band is organized into subbands used, either for uplink communications (from a user terminal REC to a moving LEO satellite and / or a GEO stationary satellite, and a passing LEO to a stationary GEO satellite), or for downlink communications (from a GEO stationary satellite to a satellite scrolling LEO and / or a user terminal REC, and a moving satellite LEO
to a user terminal REC). In this example, the L band matches substantially at frequencies between 1.518 GHz and 1.675 GHz, and:
- the sub-band used for downlink communications corresponds to frequencies between 1,518 and 1,559 GHz, - the sub-band used for upstream communications corresponds to the frequencies between 1.6265 and 1.6605 GHz, and at frequencies between 1.668 and 1.675 GHz.
The use of separate frequency subbands of the L band for uplink and downlink corresponds to a frequency multiplexing of said upstream communications and descendants, known in the Anglo-Saxon literature as Frequency Division Duplex (FDD). We also understand that others types of uplink and communications multiplexing descending, such as time or time multiplexing Duplex Division (TDD), a code division multiplexing of the type CDMA, etc. However, the use of FDD frequency multiplexing corresponds to a preferred mode of implementation because the interference between upstream and downstream communications are reduced, and because the use of TDD time multiplexing can be complex Given propagation delays inherent in telecommunications systems by satellite.
In the example shown in FIG. 5, and for a communication

19 rising, a user terminal REC transmits data in a given channel (the frequency sub-band of the L-band used for communications rising, preferably comprising several such channels) in the direction of a satellite moving LEO. Preferably, the moving satellite LEO repeats said data, transparently or regeneratively, to a satellite stationary GEO using the same channel used by the terminal REC user. As noted above, the LEO running satellite can alternatively, repeat the data in an adjacent channel of the frequency sub-band used for uplink communications.
Similarly, for downlink communication, a GEO stationary satellite transmits data in a given channel (the sub-station Band L frequency band, used for communications descending, preferably comprising several such channels) in direction of a moving LEO satellite. Preferably, the moving satellite LEO
repeats said data, transparently or regeneratively, to a REC user terminal using the same channel as the one used by the GEO stationary satellite. As previously indicated, the satellite scrolling LEO can also, alternatively, repeat the data in a channel adjacent to the frequency sub-band used for communications rising.
According to a particularly advantageous embodiment of the invention, the rising emissions, by a moving LEO satellite to a stationary satellite GEO, and downlink transmissions, by said satellite scrolling LEO to a REC user terminal are multiplexed in the weather. In other words, emissions and emissions descending by the same satellite scrolling LEO are performed during different time intervals.
Indeed, an important constraint on the design of a payload telecommunications satellite, and its cost of manufacture, comes from of the maximum instantaneous power of emission to be delivered. Due to time multiplexing of emissions and emissions downward, said maximum instantaneous emission power is reduced compared to the case of simultaneous rising and falling emissions. This is all the more advantageous as, in the case of small satellites, the instantaneous peak emission power available is usually limited (for example of the order of 60 to 150W for a mass satellite From 100 to 200 kg).
Figure 6 schematically represents a preferred mode of realizing a payload 10 of a repeating LEO satellite repeater, configured to multiplex over time the emissions rising to a satellite 10 Stationary GEO and downlink transmissions to a terminal user REC. Note that the payload 10 of the moving satellite LEO can also include other elements not shown in Figure 6.
As illustrated in FIG. 6, the payload 10 comprises a stage radio for communications with the satellite or satellites stationary GEO, called the LEO / GEO 100 floor, as well as a radio stage for the communications with the user terminal REC or said floor LEO / REC 110.
In the nonlimiting example illustrated in FIG.
LEO / GEO 100 includes four antennas 101 which are implemented at the

20 times for uplinks and for downward receptions.
A
such use of the antennas 101 for both the up and for downward receptions is made possible by the fact that these are in the same frequency band, for example in the sub-frequency bands of the L-band described with reference to FIG.
antennas 101 may be of any suitable type, for example antennas cornet, patch antennas, etc.
Each antenna 101 is coupled to two channels, a transmission channel and a reception channel, for example via a circulator 102, of known type in itself. This circulator 102 is able to route signals on the way transmission to the antenna 101, and to route signals received by the antenna towards the receiving way.
Each receive channel has a low noise amplifier or LNA 103 (acronym for Low-Noise Amplifier), which can

21 be of any type known in itself.
Similarly, the LEO / REC 110 stage comprises four antennas 111, which are implemented both for the broadcasts descending and for upward receptions, which can be of any type adapted, for example horn antennas, patch antennas, etc.
Each of the antennas 111 is coupled to two channels, one channel transmission channel and a reception channel, for example via a circulator 112, of a type known per se. Each reception channel has a low noise amplifier or LNA 113, which can be of any type known in itself.
In addition, the payload 10 comprises a power amplifier or PA 120 (acronym for the English expression Power Amplifier), which can be of any type known per se, for example an amplifier SSPA (Solid State Power Amplifier), a tube amplifier, etc.
In the preferred embodiment illustrated in FIG.
amplifier PA 120 is shared between the LEO / GEO 100 stage and the floor LEO / REC 110. In other words, the PA 120 amplifier is used both for uplink and downlink emissions. this is made possible, on the one hand, by the fact that rising emissions and downward transmissions are performed in the same frequency band, for example in the frequency subbands of the L-band described in Figure 5. This is made possible, on the other hand, by the fact that said uplinks and said downlink transmissions are multiplexed in time.
For this purpose, the payload 10 includes means for routing a signal at the output of the amplifier PA 120, representative of data to be repeated, either to the antennas 101 of the LEO / GEO 100 stage, or to the antennas 111 of LEO / REC 110. Said router means are, in the example non-limiting example illustrated in Figure 6, in the form of a switch circuit 121.
Also for this purpose, the payload 10 comprises means of to multiplex, at the input of the amplifier PA 120, emission signals rising and downlink signals. Said means of multiplexer are presented, in the non-limiting example illustrated by the figure also in the form of a switch circuit 122.

22 The payload 10 also comprises, coupled to each of the channels reception, demodulator circuits 130, of a type known per se, at the output from which are obtained two quadrature phase channels known under the name of channels I and Q. The signals obtained on each of these channels are digitized by means of analog / digital converters 131, known type, for treatment with a treatment module 150, such than a microcontroller and / or an FPGA.
The signals processed by the processing module 150, representative of the data to be repeated and in the form of two I and Q channels to phase quadrature, are converted into analog signals at the same time average of digital-to-analog converters 141. The output signals said digital-to-analog converters 141 are then provided in input of modulator circuits 140, of a type known per se, which are coupled to the switching circuit 122 at the input of the amplifier PA 120.
Moreover, without this being represented in FIG. 6, the module of processing 150 is coupled to the switch circuit 122 at the input of the amplifier PA 120 and the switch circuit 121 at the output of the amplifier PA 120. The processing module 150 is further configured to control said switching circuits 121, 122 substantially synchronized in order to use said amplifier PA 120 sometimes for the broadcasts rising, sometimes for downward transmissions.
It is understood that the interest of the preferred embodiment illustrated by the Figure 6 particularly resides in the fact that the same amplifier of power PA 120 is used sometimes for the emissions up, sometimes for downlink emissions. Indeed, it helps to reduce the number of power amplifiers to be embedded in a moving satellite LEO, which has at least the following advantages:
- power amplifiers being devices that generally consume a lot of energy, the decrease in number of power amplifiers needed allows for reduce the energy needs of the LEO running satellite,

23 the power amplifiers being devices generally bulky, the decrease in the number of power amplifiers needed to make LEO more scrolling satellites compact - this leads to LEO scrolling satellites that are less expensive to make and throw.
According to an alternative embodiment of the payload 10, also illustrated in FIG. 6, the LEO / REC 110 stage further comprises means to route a signal at the output of the amplifier PA, more particularly in output of the switch circuit 121 to any one of said antennas 111 of downward transmission.
In the nonlimiting example illustrated in FIG. 6, these means of router are in the form of a switch circuit scanning 114, for example controlled by the processing module 150 (control not shown in Figure 6).
Because of the scanning circuit 114, the payload 10 is suitable for downward transmissions, to successively activate the antennas 111. By example, if the antennas 111 are direction antennas of directions of different aiming, this allows to scan different areas on the surface of the Earth to repeat data to REC user terminals different, while emitting in each of these areas with the power instantaneous maximum emission.
Preferably, said payload 10 is configured to activate simultaneously receiving each antenna 111 of the floor LEO / REC 110. In other words, during time intervals during of which the payload 10 will perform uplink reception of data from REC user terminals, all 111 antennas will be connected by their way to the processing module 150, which will process the received signals simultaneously on each of these antennas 111. Indeed, this will allow to increase the time during which signals may be received from REC user terminals.
Nothing precludes, according to particular modes of realization, having a

24 114 more complex scanning circuit for activating simultaneously several antennas 111 (two out of four antennas, three out of four antennas, etc.), and successively activate several groups of antennas 111.
In addition, nothing excludes, according to particular modes of realization, to also provide a scanning circuit for the antennas 101 of the floor LEO / GEO 100. This can be advantageous for example to communicate with different GEO stationary satellites, the antennas 101 presenting so different aiming directions.
It should be noted that, as an alternative embodiment of the payload 10 of the FIG. 6, the same input switching circuit (coupled to the amplifier PA 120) and five outputs (four outputs respectively coupled to each of four antennas 111 of the LEO / REC 110 stage, and an output coupled to all antennas 101 of LEO / GEO 100) could be used instead of switch circuit 121 (at the output of the amplifier PA 120) and the circuit of scan 114.
According to a preferred variant of implementation of the invention, level of a moving LEO satellite, the moving LEO satellite multiplexes in the time rising emissions and upward receptions. In others terms, the moving LEO satellite does not perform uplink reception when of the intervals of time in which it performs or is likely to perform a program uplink.
Preferably, the moving LEO satellite also multiplexes in the time downward transmissions and downward receptions. In others terms, the LEO traveling satellite does not perform downward intervals of time in which it performs or is likely to perform a downlink broadcast.
According to the invention, communications between user terminals REC and LEO traveling satellites, and for communications between LEO traveling satellites and GEO stationary satellites, use a even frequency band.
More particularly, if we place ourselves in the non-limiting example illustrated in Figure 5, uplink communications use a first frequency subband of the L band, while communications descendants use a second frequency sub-band of the L-band.
It is therefore understandable that, from a point of view of the satellite parading LEO, a rising broadcast to a stationary GEO satellite could disrupt a simultaneous uplink reception carried out by this moving LEO satellite, in the extent that these communications are performed in the same subband of frequency of the L-band. This is also the case from the point of view of satellite scrolling LEO, for a simultaneous downlink broadcast at a reception downlink made by this satellite parading LEO.
10 From such disturbances could be reduced by isolating the floor LEO / GEO 100 from the LEO / REC 110 stage, but this isolation would be accompanied by addition of additional isolation devices and / or removal increased antennas 101 of the floor LEO / GEO 100 and antennas 111 upstairs LEO / REC 110. Multiplexing over time, at the moving satellite 15 LEO, rising emissions and upward receptions on the one hand, downward transmissions and downward receptions on the other hand, such disturbances are removed. This deletion is achieved without having to add additional insulation devices. In addition, antennas 101 of the LEO / GEO 100 stage and the LEO / REC 110 level antennas 111 can be closely spaced, for example arranged on adjacent faces of the satellite scrolling LEO.
It should be noted that time-division multiplexing, at the level of a satellite scrolling LEO, rising and rising shows on the one hand,

25 and downward transmissions and downward receptions on the other hand greatly simplifies the design of the LEO / GEO 100 and LEO / REC 110 from an electromagnetic isolation point of view. Such provisions could therefore be considered independently of the time multiplexing of emissions and emissions descendents, which allow a better sharing of the power on board on board the LEO running satellite.
However, we understand that the combination of time division multiplexing uplink and downlink emissions, and multiplexing

26 the time of rising and rising transmissions on the one hand, and downward transmissions and downward receptions on the other hand, allows the design of particularly compact LEO scrolling satellites and with a better controlled cost.
Figures 7a and 7b illustrate two examples of implementation.
In these examples, F1 has been designated as the frequency sub-band used for uplink and by F2 the subband of frequency used for downlink communications.
It should be noted that the examples illustrated in FIGS. 7a and 7b are place from the point of view of the moving LEO satellite. We note in particular points following:
a rising arrow F1 between a user terminal REC and a scrolling satellite LEO indicates a time interval during the moving LEO satellite is receiving a reception in the F1 band. The absence of such a rising arrow F1 means that said LEO traveling satellite does not perform reception in the sub-station.
F1 band, but does not imply that the REC user terminal does not transmit a signal in said sub-band F1; in particular, if conditions permit, the REC user terminal can send a signal directly to the stationary satellite GEO (the coexistence of the signals emitted in the F1 sub-band by the user terminal REC and the moving satellite LEO being able to do for example with a CDMA air interface and use of a Rake receiver at the GES ground station);
a down arrow F2 between a stationary satellite GEO and a scrolling LEO satellite indicates a time interval during the moving LEO satellite is receiving a reception in the F2 band. The absence of such a downward arrow F means that said LEO traveling satellite does not perform reception in the sub-station.
F2 band, but does not imply that the stationary GEO satellite does not transmit a signal in said sub-band F2; in particular, if conditions permit, the GEO stationary satellite can

27 send a signal directly to the user terminal (the coexistence of the signals transmitted in the subband F2 by the GEO stationary satellite and the LEO running satellite capable of do for example with a CDMA air interface and use of a Rake receiver at the user terminal REC).
In the example illustrated by FIG. 7a, time division multiplexing, at level of a moving LEO satellite, is organized around three time intervals 11, 12 and 13.
During a first time slot 11, the satellite moving LEO
performs downlink transmissions in the F2 sub-band towards a or several REC user terminals.
During a second time interval 12, the LEO scrolling satellite makes the rising emissions in the F1 sub-band towards one or of several GEO stationary satellites.
During a third time slot 13, the satellite moving LEO
simultaneously performs uplink receptions in the F1 sub-band and downward receptions in the F2 sub-band.
This sequence of time intervals 11, 12 and 13 is preferably performed recurrently. For example, the duration of each of these time intervals may be predetermined fixed value, or variable at determine according to predefined criteria. For example, the duration of each these time intervals may be between a few tenths of second and a few tens of seconds.
In a preferred embodiment, and as illustrated in FIG. 7b, payload 10 is configured to perform uplinks simultaneously with downward transmissions, and to perform receptions descending simultaneously to rising emissions.
As illustrated in Figure 7b, time division multiplexing is then articulated mainly around two time intervals 11 and 12.
During a first time slot 11, the satellite moving LEO
performs downlink transmissions in the F2 sub-band towards a

28 or several REC user terminals, as well as uplinks in the sub-band F1 of signals possibly emitted by one or more REC user terminals.
During a second time interval 12, the LEO scrolling satellite makes the rising emissions in the F1 sub-band towards one or of several GEO stationary satellites, as well as receptions downward in the sub-band F2 of signals possibly emitted by a or stationary GEO satellites.
This sequence of time intervals 11 and 12 is preferably performed recurrently. For example, the duration of each of these time intervals can be predetermined fixed value, or variable to determine according to predefined criteria. For example, the duration of each these time intervals may be between a few tenths of second and a few tens of seconds.
FIG. 8 represents a variant embodiment of the payload of FIG.
FIG. 6, adapted for satellite payload operation LEO scrolling repeater as shown in Figure 7b.
With respect to the payload 10 illustrated in FIG. 6, a larger number of components are used both for communications with a or more GEO stationary satellites and for communications with a or more REC user terminals.
This is made possible by the fact that these communications, from view of the LEO moving satellite, are multiplexed in time, as the points out Figure 7b.
Thus, with respect to the payload 10 illustrated in FIG.
following components are shared:
the modulator circuits 140: the sharing of these components allows to reduce the number from two to one, - the digital-to-analog converters 141: the sharing of these components can reduce the number from four to two, the demodulator circuits 130: the sharing of these components reduces the number from eight to four,

29 the analog / digital converters 131: the sharing of these components can reduce the number from sixteen to eight.
With respect to the payload 10 of FIG. 6, the circuit switch 122 at the input of the amplifier PA 120 has been removed, the multiplexing being performed directly by the processing module 150.
On the other hand, switching circuits 160 have been added as input demodulator circuits 130, controlled by the processing module 150 (not shown in the figure), in order to connect them to both upstairs LEO / GEO 100 and upstairs LEO / REC 110.
It is therefore understandable that, because of the use of the same band of frequency and because of the time multiplexing of communications with the stationary satellites and communications with terminals users, he possible to obtain a particularly optimized payload.
It should be noted that other components may also be shared, such as LNA amplifiers 103, 113.
Advantages of the invention Thanks to the combination of a constellation of LEO traveling satellites (which makes it possible to provide a more efficient service to the polar regions) and a constellation of stationary satellites GEO (which provides a quality equatorial regions and at low latitudes), the average duration of no visibility of a satellite for a user terminal is canceled or greatly reduced compared to the systems of the prior art, in particular when high angles of elevation are sought (in the case of mobile satellite communications the signal blocking factor is reduced high rise which leads to a better availability of the service).
It will be understood that a system as described makes it possible to offer a significantly increased availability (through near-continuous coverage) for users who have to evolve in remote areas covered by traditional communications systems. This is the case example for polar areas, through a constellation in orbit polar or quasi-polar).
In addition, multiplexing adapted to different tasks transmission / reception of the payloads of the LEO traveling satellites to greatly simplify the design and reduce the cost of manufacturing, everything maintaining a high level of performance.
Other advantages of the invention appear particularly well When compared to existing solutions, using either satellites in low orbit, either geostationary satellites or constellations hybrids.
Compared to a satellite communications solution employing a constellation of satellites in low orbit (such as Orbcomm or Argos by For example, the advantages provided by the invention are multiple:
- it is not necessary to deploy connection stations for communications between LEO's moving satellites and terrestrial network infrastructure; indeed, the connection station GEO stationary satellites guarantee access Permanent to LEO scrolling satellites;
- it is not necessary to deploy radio stations Remote Control / Telemetry & Control (TT & C) of the constellation satellites, TT & C signals being also relayed by the stationary GEO satellite or satellites; we understand 20 control of the LEO moving satellites is carried out, since the ground, by the stationary GEO satellite control stations, at through these stationary GEO satellites;
- a clearly simplified LEO scrolling satellite design from made of a payloads operation of these satellites 25 LEO scrollers to share the power on board between high and low emissions, and to reduce the need for electromagnetic insulation between LEO / GEO floor and LEO / REC floor.
Compared to a satellite communications solution employing a

Satellite in geostationary orbit, the benefits provided by the invention are:
- an extension of the coverage of the GEO stationary satellite for cover for example the polar areas, - reduced latency for network access and for

31 Acknowledgment of receipt.
Compared to a system (included in the state of the art) of hybrid satellite telecommunications comprising one or more satellites in geostationary orbit and a constellation of satellites in low orbit, the advantages provided by the invention are:
- the use of a common protocol between the two systems, plus effective as each protocol taken separately.
- a pooling of the frequency band used, with mechanisms ensuring that intra-system interference is limited.
Because of its design, the concept is particularly adapted to user terminals with low directivity and not requiring the maintaining pointing towards satellites in low orbit. Indeed, he the user terminal points to a GEO stationary satellite or scrolling LEO to ensure communication.
The applications envisaged concern the improvement of future mobile satellite systems in geostationary orbit (MSS or Mobile Satellite Services), including aeronautical mobile services by satellites such as AMSS (Aeronautical Mobile Satellite Service) and AMSRS
(Aeronautical Mobile Satellite Route Services), in UHF band, L, S, C or X

relying on the deployment of a low-orbit constellation much less complex than existing MSS constellations (such as Globalstar or Iridium) for voice, data or exchange type communications machine-to-machine (M2M) messages.
This concept can also be applied to broadcast systems mobile satellite data, television or radio (eg broadcast S-DAB standard radio using an L-band BSS allocation or the DVB-SH standard mobile TV broadcast using MSS allocation in S-band).
Another use of this concept concerns data exchanges for navigation applications (maritime or aeronautical, in particular).
In these applications, known to those skilled in the art under the name SBAS (from

32 the English Satellite Based Augmentation System), it does not exist currently means to cover the mobile terminals located in the vicinity of the poles.
The invention overcomes this problem with a satellite in orbit geostationary, and a satellite in low orbit scrolling in view of the mobile.
Similarly, within a service area of a satellite geostationary there are some shadow areas for which the satellite geostationary is not in line of sight of the surface terminals at cause masking phenomena by buildings or natural elements (trees, mountains, ...). Coverage of a shadow zone of these devices traditional communication is possible, provided that this zone can come in view of a moving satellite in low orbit.
The use of a telecommunications system or process, according to the invention therefore makes it possible to extend the coverage area of means of communication with areas of darkness, and in particular to extend the coverage area of an SBAS system using a satellite geostationary.
In the case where the space repeater transmits in an adjacent channel to the stationary GEO satellite and regeneratively, an asset of the invention concerns the possibility of a possible simplification of the protocols exchanges between the user terminals and the LEO traveling satellites.
The LEO traveling satellites can notably perform a conversion to a specific exchange protocol for GEO (to for example, propagation delay constraints specific to the GEO), or aggregation of messages and optimization of the use of bandwidth.
Another important attraction of this concept is the possibility of having a permanent and almost real-time link between the control network and mission and constellation of LEO traveling satellites through the station of connection and relay GEO.
It is also understood that the system does not require mandatory deployment of a constellation of LEO traveling satellites or dedicated GEO stationary. It is indeed possible to use capacities of

33 transmission available on stationary satellite constellations GEO
already existing.
In this case, we naturally choose the frequency band of the constellation of GEO stationary satellites used as a working frequency of LEO traveling satellites. This solves the problem problem of the few available frequency bands for services mobile satellites using non-geostationary satellites, and this offer therefore a regulatory interest in deploying a constellation of LEO running satellites operating on a secondary basis in the same band frequency than the stationary GEO satellites.
Likewise, the functions envisaged for LEO traveling satellites can actually be done using embedded payloads as passengers on LEO traveling satellites dedicated mainly to other functions. In this case, the decisive criterion is the envisaged orbit for the LEO moving satellite. An advantageous choice is that of satellites observing the Earth, which frequently use a sun-synchronous orbit very inclined, and thus covering high latitudes.
This implementation of the payloads as passengers, and naturally very advantageous in terms of the cost of deploying the system.
The system described here is therefore a simple solution and economic in comparison with other possible alternatives such as:
- the deployment of a large number of ground stations to offer a permanent connection between the LEO traveling satellites and the ground, which is a costly and complex solution to implement in particular to cover the oceans (the Globalstar constellation is a good illustration of this difficulty);
- the use of inter-satellite links to provide a connection between the LEO moving satellites and a limited number of ground stations; this solution has the disadvantage of adding complexity and additional cost in the space segment (the Iridium constellation is a good illustration of this solution).
Finally, the advantageous and less expensive architecture of the payload,

34 as described previously, can reduce the cost of the system without sacrifice his performances. In this case, the significant reduction in complexity of the satellite platforms repeaters scrolling used allows of lower their price and / or increase the number of satellites deployed in the telecommunications system.
Variants of the invention The use of spatial diversity (or MIMO techniques) in user terminal level to recombine the signals from both of the GEO stationary satellite and the LEO moving satellite can be envisaged to improve the link budget further.
The satellite repeater can be a simple analog repeater transparent which is the simplest solution but imposes constraints on the air interface so as to limit interference at the of between the signals coming from the GEO stationary satellite and the signals relayed by the moving LEO satellite.
An alternative solution is to relay the signal (so transparent or regenerative) in a channel of the same frequency band on board the repeater satellite. This solution requires an entity of coordination to coordinate frequency plans between GEO stationary satellites and LEO scrolls.
The relay satellite constellation can also implement additional features (store & forward, signal aggregations).
The constellation of repeater satellites can offer coverage or part of the Earth according to the objectives.
The constellation of repeater satellites can offer coverage continuous in time (for real-time services available at any instant) or only access with a certain delay (for services not real time) using constellations with a reduced number of satellites.
It is also clear that the concept described, using the same band of frequency for communications between surface terminals and repeater satellites and for communications between repeater satellites and Stationary satellites, can only be applied on the one-way or on the return lane or both ways.

Claims (14)

35 1 - Payload of satellite repeater (LEO) of a system of telecommunications said repeater satellite being intended to be placed in moving orbit above of the Earth's surface, and the payload being configured to repeat of the data received from a stationary satellite (GEO) above the surface of the Earth to a terminal (REC) substantially on the surface of the Earth, and for repeating data received from the terminal to the stationary satellite, said payload comprising at least one power amplifier and being additionally configured for:
- use the same frequency band for data repetition towards the stationary satellite (GEO), so-called rising emission, and for the repetition of data to the terrninal (REC), said emission downlink, said frequency band being any of the VHF, UHF, L, S, C, X, Ka, Q bands, - carry out the rising and falling emissions at course of different time intervals, - use said power amplifier for both broadcasts rising and for downward transmissions. 2 - payload according to claim 1, comprising:
- at least one rising transmission antenna, - to motels a downward transmitting antenna, means for routing a signal at the output of the amplifier of power, representative of data to be repeated, or to said antenna transmitting upstream to said downward transmitting antenna. 3 - Payload according to claim 2, comprising means for multiplex, at the input of the power amplifier, signals emissions rising and downlink signals. 4 - payload according to any one of claims 1 to 3, comprising:
- several downward transmitting antennas, means for routing a signal at the output of the amplifier of power, representative of data to be repeated, towards any one said downward transmitting antennas. - payload according to any one of claims 1 to 4, wherein said payload is configured to use the same frequency band, used for both upline and downlink emissions, for the reception of data to be repeated from the terminal (REC), said reception rising, and for receiving data to be repeated from the satellite stationary (GEO), called downward reception. 6 - payload according to claim 5, comprising several antennas of uplink reception, said payload being configured to receive simultaneously on each of said uplink receiving antennas. 7 - payload according to claim 5 or 6, wherein said load useful is configured to multiplex over time the emissions and receptions, and / or to multiplex over time the broadcasts descending and descending receptions. 8 - payload according to any one of claims 5 to 7, in which said payload is configured to use the same first frequency band of the frequency band for the upward receptions and uplinks, and use the same second subband of Frequency band frequency for downward and downward downlink emissions. 9 - payload according to any one of claims 5 to 8, in which said payload is configured to perform uplinks simultaneously with downward transmissions, and to perform receptions descending simultaneously to rising emissions. - Telecommunications system for data transfer between least one terminal (REC), located substantially on the surface of the Earth, and minus a stationary satellite (GEO) above the surface of the Earth, comprising one or more signal repeater satellites (LEO), repeater satellites parading over the surface of the Earth and comprising a payload according to any one of claims 1 to 9. 11 - Telecommunications method, intended for the transfer of data between a terminal (REC), located substantially on the surface of the Earth, and a satellite stationary (GEO) above the surface of the Earth, the transfer of data between said terminal and said stationary satellite being effected by via a repeater satellite (LEO) configured to repeat data received from said stationary satellite to said terminal and to repeat data received from said terminal to said stationary satellite, in which the satellite repeater (LE0):
- uses the same frequency band for data repetition towards the stationary satellite (GEO), so-called rising emission, and for the repetition of data to the terminal (REC), said transmission downlink, said frequency band being any of the VHF, UHF, L, S, C, X, Ka, Q bands, - performs both high and low emissions courses of different time intervals, and - uses the same power amplifier for transmissions rising and for downward transmissions. 12 - Process according to claim 11, wherein the repeater satellite (LEO) uses the same frequency band, used for uplink and downward transmissions, for receiving data to be repeated from terminal, so-called uplink reception, and for receiving data at to repeat the stationary satellite, called downward reception. 13 - Process according to claim 12, wherein the satellite repeater (LEO) multiplexes over time the emissions and receptions uplinks, and / or said repeater satellite (LEO) multiplexes in time the downward transmissions and downward receptions. 14 - The method of claim 12 or 13, wherein the satellite repeater (LEO) uses the same first frequency subband of the band of frequency for uplinks and uplinks, and uses the same second frequency sub-band of the band of frequency for downward and downward transmissions.